The present invention relates to a method for processing fruits, grains, vegetables, and tubers, in particular potatoes, to produce dehydrated products.
Farinaceous products comprising dehydrated fruits, grains and vegetables, in particular potatoes, have become extremely popular. Among the most popular products are fabricated potato chips, tortilla chips, pretzels and extruded or puffed products. Farinaceous products are generally made by adding ingredients such as, water, flavoring, emulsifiers and other starch materials to a dehydrated product. The mixture is then typically extruded and/or sheeted and cooked (e.g., baking, frying) to form the final product. Control over the taste and other organoleptic properties of the finished product is largely dependent on the physicochemical and organoleptical properties of the starting dehydrated product.
Among the most popular dehydrated products included in the preparation of farinaceous products are dehydrated potato flakes, flanules, and granules. Two basic processes are employed to produce dehydrated granules, flanules and dehydrated potato flakes. The initial preparation for both processes is typically the same. Raw potatoes are washed, peeled, and inspected to remove any defective potatoes. The good potatoes are cut into slabs, rinsed with room temperature water, and fed into the cooking operation, which is divided into two cooking steps. The first cooking step is a pre-cook step which partially cooks the potato at about 155xc2x0 F. to about 175xc2x0 F. (the activation temperature at which hydrolysis of protopectin can occur) and solubilizes some of the starch. During this step, swelling and gelatinization of the starch starts to occur. Following the pre-cook, the potatoes are cooled in water which causes the solubilized starch to precipitate out of solution, also known as retrogradation. In the case of flanules, and in the case of some types of flakes (i.e. some flakes used to produce fabricated snacks), the precooking and cooling steps are omitted. The second cooking step involves cooking the potatoes in a steam cooker that gelatinizes the starch and prepares the potatoes for dehydration. After this point in the process, the granule and flanule process differ from the flakes process. The granules and flanules process differs from the flake process in that the drying step is gentler and does not destroy potato tissue as does the drum drying that is more commonly used in the flaking process. Drum drying relies primarily on conduction heat transfer, which can be inefficient and detrimental to product quality. In the case of flanules, the drying operation includes fluidization and air lift drying, which are both based on convection heating.
Secondly, the dehydration step is much slower, causing retention of potato granules in the system for long periods. Thirdly, the granulation procedure differs from the flaking process in the drying procedure employed, whereby a portion of the granules, which are first dried, are recycled back into the stream of cooked mashed potatoes. This procedure is known as the add-back process.
Conventional methods for processing potatoes into dehydrated products have certain disadvantages. In the conventional processes for making potato flakes and granules, the potatoes are subjected to pre-cooking, cooling, cooking, and a number of other steps that reduce and change the original potato flavor and starch functional properties. Typically, the potatoes are washed, peeled, blanched, precooked and cooled before the cooking step. The potato slices are generally transported by water. This requires a substantial use of water and energy. The steps of water pre-cooking and cooling result in substantial loss of water soluble flavor precursors (or flavor components) and various aqueous phase reactions that degrade the taste and quality of the dehydrated product. Additionally, a considerable loss of the positive volatile flavor components can occur during drying. From an economic standpoint, these processes require a considerable expenditure of energy, time, and money in the pre-cooking, cooling, cooking, and drying steps. In addition to loss of flavor, from up to about 10% of the potato product can be lost during peeling. During the step of peeling of potatoes, high steam pressure is used to soften the skin from the potato tissue. This forms the so called xe2x80x9cpeel ringxe2x80x9d, which is a thin layer of cooked starch surrounding the potato. Later during cooking this thin layer represents swollen starch which delays the heat transfer rate to the center of the potato pieces, causing uneven cooking of potatoes, resulting in a combination of raw potato pieces and overcooked potato pieces.
Another disadvantage of conventional processes for dehydrating potatoes arises because of the relatively long cooking time (up to about 45 minutes) needed to thoroughly cook the raw potato. The consequence of slow cooking is also the substantial use of energy needed to cook the raw product. Such prolonged cooking time of the potato destroys vitamins, reduces initial concentration of desirable flavor precursors, contributes to the formation of processed flavors, and increases cell damage.
A further disadvantage of conventional processes is that they can not be used efficiently to produce consistent quantities of high quality potato flakes, flanules, and granules suitable for use in farinaceous products. Additionally, in most cases the primary processes are not designed to produce flakes or granules having the characteristics suited, to say extrude or form a sheetable dough, but rather aimed at producing an ingredient for a completely different use such as rehydration for table use (e.g., mashed potatoes), or low shear forming potatoes for intermediate moisture products, such as, potato pancakes or French fries.
Accordingly, it is an object of the present invention to provide an efficient method for dehydrating fruits, vegetables, and grains, in particular potatoes, based on energy consumption and potato losses.
Another object of the present invention is to provide a process for making dehydrated potato products which enhances cooking to obtain key material transformations, while resulting in significantly shorter cooking residence times, and improved quality.
It is another object of the invention to provide a method for producing high quality, low cost dehydrated potato products using a method that is simple, quick and economical.
Still another object of the present invention is to provide a process for making dehydrated potato products, which eliminates the need for precooking and cooling of the raw potatoes.
It is another object of the present invention to provide dehydrated potato products particularly suitable for use as part of the dough used to make fabricated farinaceous products such as fabricated potato snack pieces.
It is further an object of the present invention to provide dehydrated potato products having improved nutritional value, color and processing quality over conventionally produced flakes, flanules, or granules.
It is further an object of the present invention to provide dehydrated products having an increased level of flavor precursors as compared to conventionally produced products.
It is another object of the present invention to provide dehydrated potato products particularly suitable for use in providing reconstituted mashed potatoes with improved flavor, texture, and shelf life.
These and other objects of the invention will become apparent from the following disclosure and claims.
In accordance with the present invention, an improved method of producing dehydrated products is provided. While the invention is particularly useful in preparing dehydrated potato products, it is also useful in preparing other dehydrated products such as fruits (e.g., bananas, pears, apples, peaches, apricots) and vegetables (e.g., sweet potatoes, beets, pumpkin), and grains such as corn products (e.g.. masa), wheat, oat, barley, sago, amaranth, and cassava.
The present invention is primarily concerned with (1) substantially eliminating the pre-cooking, cooling and optionally peeling steps, (2) substantially reducing the cooking time by a) augmenting functional characteristics typically achieved by extended cooking, for example release of free amylose, by adding exogenous sources such as wheat starch or potato starch, b) and/or basing the minimum cooking time on the energy needed to partially gelatinize the starch, inactivate the enzymes responsible for enzymatic browning, and activate the enzyme responsible for cell separation and partial hydrolysis of the protopectin, resulting in softening of the tissue, c) and varying the size of potato pieces, and (3) reducing the drying time of the raw product by enhancing drum drying with infrared heating. This results in flakes having improved physicochemical properties, flavor, nutritional and appearance (e.g. lighter color) benefits.
According to one embodiment of the present invention, a method for preparing a starch containing product is provided. The method comprises the steps of: providing a starch containing material comprising one or more enzymes capable of causing browning, lipid oxidation, or hydrolysis of cellulosic material; partially cooking the starch containing material for a predetermined amount of time and temperature sufficient to substantially inactivate one or more of the enzymes to reduce enzymatic browning, activate the enzyme responsible for partial hydrolysis of cellulosic material, enable cell separation, at least partially gelatinize the starch, and maintain breakage of starch cells to less than about 70%, preferably to less than about 40%, and more preferably to less than about 20%; comminuting the partially cooked starch containing material to produce a wet mash; and drying the wet mash to produce a dehydrated product having a moisture content below about 15% on a fat free basis.
According to another embodiment of the present invention, another method for preparing a starch containing product is provided. The method comprises the steps of: providing a starch containing material containing sugars of any other components having the ability to produce non-enzymatic browning; partially cooking the starch containing material for a predetermined amount of time and temperature sufficient to at least partially gelatinize the starch and maintain breakage of starch cells to less than about 70%, preferably to less than about 40%, and more preferably to less than about 20%; comminuting the partially cooked starch containing material to produce a wet mash; and drying the wet mash to produce a dehydrated product having a moisture content below about 15% on a fat free basis.
The starch containing material can comprise polyphenol oxidase, and the step of partially cooking the starch containing material can comprise cooking the starch containing product for sufficient time to substantially inactivate the polyphenol oxidase without completely gelatinizing the starch. The starch containing material can also comprise one or more materials capable of causing non-enzymatic browning. The starch containing material can comprise protopectinase, and the step of partially cooking the starch containing material can comprise cooking the starch containing material for sufficient time to substantially activate the protopectinase without completely gelatinizing the starch.
The step of partially cooking the potatoes can comprise cooking for a time sufficient to produce potatoes having a center texture value of from about 20 gf to about 1000 gf, preferably from about 100 gf to about 500 gf.
The product may be cooked by water immersion, steam, a combination of water immersion and steam, or microwave for a time sufficient to: partially gelatinize the starch such that, if desired, complete gelatinization can occur during subsequent process steps (e.g., drying, frying, baking, or extrusion); inactivate the enzyme (e.g., polyphenol oxidase) responsible of browning; and activate the enzyme responsible for cell separation through partial hydrolysis of protopectins (protopectin is an insoluble, highly polymerized form of pectin associated with the cell wall structure) resulting in softening of the tissue. The product can be comminuted, and then dried. The comminuted product may be dried using various drying methods, for example, drum drying, infrared drying, a combination of infrared and drum drying, freeze drying, fluidized bed drying, air-lift drying, or combinations thereof.
The method can further comprise the step of adding an additive or any material including dry flakes to the wet mash prior to the drying step, wherein the additive is effective in altering the rheology of the mash. The additive is effective in altering the viscosity of the mash, and can be effective in supplementing the free amylose and/or amylopectin content of the mash. In one embodiment, the additive can comprise an unmodified starch to the wet mash prior to the drying step and wherein the starch is selected from the group consisting of wheat starch, corn starch, tapioca, rice starch, potato starch, oat starch, sago starch and mixtures thereof.
The method can further comprise the step of adding chemical reagents to produce chemical modification of potato starch in the flakes (i.e. succinylation, acetylation, phosphorilation, etc.). This will result in cross-linked potato starch in the flakes, or substituted, or other modification. The additive could have the objective of altering the pH of the mash (i.e. calcium hydroxide, hydrocholoric acid, citric acid, etc.).
According to another embodiment of the invention, a method is provided for drying a material to form a dehydrated product. The method comprises: (a) providing a wet mash comprising the material to be dried; (b) drying the wet mash wherein drying the wet mash comprises the step of
(i) providing a first energy source selected from the group consisting of conductive heat sources, convective heat sources, infrared energy sources, and combinations thereof;
(ii) providing a second energy source comprising a source of infrared energy;
(iii) forming a layer of the wet mash, the mash layer having a first surface and an oppositely facing second surface;
(iv) heating the first surface of the mash layer with the first energy source; and
(v) heating the second surface of the mash layer with the second energy source;
wherein the mash is dried to a moisture content of less than about 50 percent by weight prior to heating the second surface of the mash layer;
and wherein at least a portion of the steps of heating the first and second surfaces of the mash layer are carried out simultaneously.
In one embodiment, the first energy source is a steam heated drum dryer. The first surface of the mash can be disposed on a heated drying surface of the drum dryer and the oppositely facing second surface of the mash is heated by the infrared source.
According to another embodiment of the present invention, dehydrated potato flakes are provided. The dehydrated potato flakes have an Average Vitamin C Retention Rate of at least about 7% relative to the Vitamin C initially present in the potato material from which the potato flakes are formed; and the flakes have a Relative Absorbence Index of less than about 1.5.
The dehydrated potato flakes can have a color corresponding to a xe2x80x9cLxe2x80x9d value greater than about 78 Hunter units, a xe2x80x9cbxe2x80x9d value less than about 21 Hunter units, and an xe2x80x9caxe2x80x9d value of from about xe2x88x921 to about xe2x88x923 Hunter units. The flakes can comprise up to about 0.3 ppm, preferably from about 0.1 to about 0.3 ppm, of 2-methylpyrazine; and up to about 2.7 ppm, preferably up to about 1.5 ppm, of phenylacethaldehyde; and up to about 0.7 ppm, preferaby from 0.1 to 0.6 ppm, of methional; and have a free amylose content of from about 20 to about 38%.
The flakes can be used to form a dough having a modulus of elasticity (Gxe2x80x2) of from about 15000 Pascals to about 90000 Pascals, preferably from about 35000 Pascals to about 55000 Pascals; and a viscosity modulus (Gxe2x80x3) from about 3000 Pascals to about 15000 Pascals, preferably from about 5000 Pascals to about 10000 Pascals. In one embodiment of the present invention, the flakes and corresponding dough can be used to make fabricated snack products.
An important advantage of the present invention is a reduction in product losses and an increase in production rate over conventional processes. Another advantage of the present invention is elimination of the pre-cooking, cooling, and preferably the peeling step, thereby significantly reducing cooking time and residence time during drying. This reduces cost and removes expenses associated with high energy and high water usage hereto for encountered by the processing industry. Reduction of cooking time in combination with no peeling of potatoes increases production rate in the flaking process. This is due to the fact that potato peeling is still attached to the potato tissue when it is partially cooked, and no peel ring has been formed. This causes the peel to stick more to the drum drier and to the mashed potatoes, and increases the production in terms of lbs/hr. In the current flaking industry, when unpeeled overcooked potatoes are processed, the peel normally separates from the mash during drum drying through the last applicator roll, causing an increase in potato losses.
Still another advantage of the present invention is that the dehydrated product has less formation of degradation products and retains more nutrients (such as Vitamin C), more flavor precursors, and more total amino acids than a corresponding product obtained by conventional methods. A further advantage of the present invention is that it provides a product having improved color retention, less processed flavor and less cell breakage. Without being limited by theory, it is believed that this is due to a) inactivation of polyphenol oxidase and b) reduction of the non-enzymatic browning reaction rate and the residence time of the mash during cooking and drying. The term non-enzymatic browning reaction refers to the reaction wherein a reducing sugar containing material, when heated alone or in the presence of amino acids, peptides, and proteins, can result in the production of dark brown melanoidins and other compounds, some of which impart undesirable flavor.
Reduction of cell breakage is due to shorter residence time during cooking and drying. Less cell damage results in a decrease of compounds leaching from the cell (e.g. flavor precursors and nutrients such as vitamins).